The present invention relates to a process for the high speed production of pre-oriented yarns from synthetic linear polymers, in particular polyesters but others as well, as for instance polyamides.
It is known in the art to produce partially oriented, generally called "pre-oriented", yarns which are used as raw material for further textile processing by, melt spinning and winding-up at a relatively high speed. For instance, in Belgian Pat. No. 787,882 there is described a process for preparing a texturized yarn, in which a feed yarn is employed which is constituted by a polyester yarn spun with a wind-up speed between 2560 and 4100 meters per minute (hereinafter expressed as m/1'). In this process the yarn must be wound-up at a speed which exceeds a certain minimum in order to obtain a significant and desired degree of pre-orientation, but on the other hand, it cannot be wound-up at a speed that exceeds a certain maximum, because otherwise, the orientation would be excessively pronounced and practically complete, and the yarn would not be equally suitable for the successive textile treatments, as for instance texturization.
It is evident that it is technically desirable to carry out any process at the highest possible speed in order to increase the productivity of the available equipment. On the other hand, it is possible to build, without excessive difficulties, yarn winding-up groups which operate at winding-up speeds significantly higher than the 4100 m/1' indicated as a maximum in the aforesaid patent.
Finally, if it is desired to submit the yarn obtained to further treatments, for instance texturization and drawing as in the aforesaid patent, the characteristics of the yarn cannot be varied as desired according to the winding-up speed, but must be maintained substantially unchanged if the final use is the same.